javaWeb 实现上传+下载文件

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上传下载在web项目中应该是很常见的需求，能够熟练敲出代码实现是web开发人员必不可少的

下面简化的上传：

jsp页面的实现：

[html] view plain copy print?

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core" prefix = "c" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'uploadfile.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<form action="<c:url value = '/UploadServlet1' />" method="post" enctype="multipart/form-data" >
用户名：<input type = "text" name = "username">
上传照片：<input type = "file" name = "photo">
<input type = "submit" value="提交">
</form>
</body>
</html>

servlet的实现:

[java] view plain copy print?

package cn.Lionel.servlet;
import java.io.File;
import java.io.IOException;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
public class UploadServlet1 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
//创建工厂
DiskFileItemFactory factory = new DiskFileItemFactory() ;
//通过工厂创建解析器
ServletFileUpload upload = new ServletFileUpload(factory);
try {
List<FileItem> list = upload.parseRequest(request);
FileItem item1 = list.get(0);
FileItem item2 = list.get(1);
System.out.println("普通表单项："+item1.getName()+"="+item1.getString("utf-8"));
System.out.println("文件表单项:");
System.out.println("Content-Type"+item2.getContentType());
System.out.println("filename="+item2.getName());
System.out.println("size = "+item2.getSize());
item2.write(new File("d:\\1.jpg"));
} catch (Exception e) {
throw new RuntimeException() ;
}
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}

下面是设置了缓存文件夹+文件打散

jsp页面跟上面差不多：

[html] view plain copy print?

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core" prefix = "c" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<title>My JSP 'uploadfile.jsp' starting page</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<!--
<link rel="stylesheet" type="text/css" href="styles.css">
-->
</head>
<body>
<h1>${msg }</h1>
<form action="<c:url value = '/UploadServlet2' />" method="post" enctype="multipart/form-data" >
用户名：<input type = "text" name = "username">
上传照片：<input type = "file" name = "photo">
<input type = "submit" value="提交">
</form>
</body>
</html>

servlet的实现依赖commons.fileupload组件

[java] view plain copy print?

package cn.Lionel.servlet;
import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.UUID;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadBase;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
public class UploadServlet3 extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
//设置缓冲区和临时目录
DiskFileItemFactory factory = new DiskFileItemFactory(100,new File("e:\\temp"));
ServletFileUpload upload = new ServletFileUpload(factory);
//限制上传的文件大小
//upload.setFileSizeMax(200*1024) ;
//限制整个表单的大小：upload.setSizeMax();
try {
List<FileItem> list = upload.parseRequest(request);
FileItem item = list.get(1);
String filename = item.getName();
//处理有些浏览器返回的文件名是绝对路径
int index = filename.lastIndexOf("\\") ;
if(index != -1)
{
filename = filename.substring(index+1);
}
int hashCode = filename.hashCode();
//把hash值转换为十六进制
String hex = Integer.toHexString(hashCode);
String realPath = this.getServletContext().getRealPath(
"WEB-INF/files");
File dirFile = new File(realPath + "/" + hex.charAt(0) + "/"
+ hex.charAt(1));
//创建目录链
dirFile.mkdirs();
String savename = uuid()+"_"+filename;
File destFile = new File(dirFile,savename);
item.write(destFile);
}catch (FileUploadException e) {
if(e instanceof FileUploadBase.FileSizeLimitExceededException)
{
request.setAttribute("msg", "您上传的文件超出200KiB!") ;
request.getRequestDispatcher("/uploadfile2.jsp").forward(request, response) ;
return ;
}
}
catch (Exception e) {
throw new RuntimeException();
}
}
private String uuid() {
return UUID.randomUUID().toString().replace("-", "").toUpperCase();
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}

说完了上传，该说下载了：

该事先依赖commons.io组件，直接访问servlet实现下载。要下载的文件需要改你自己项目中存在的文件。

[java] view plain copy print?

package cn.Lionel.servlet;
import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.io.IOUtils;
import sun.misc.BASE64Encoder;
public class DownloadServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset = utf-8");
String filename = "E:\\KuGou\\可米小子 - 青春纪念册.mp3"; //改为自己项目中存在的文件
//这种方法对部分字符仍存在乱码！
//String dname = new String("青春纪念册.mp3".getBytes("utf-8"), "iso-8859-1");
//这种方法最常用！解决文件名乱码
String dname = filenameEncoding("青春纪念册.mp3",request);
String contentType = this.getServletContext().getMimeType(filename);
String contentDisposition = "attachment;filename="+dname;
response.setHeader("Content-Type", contentType + "");
response.setHeader("Content-Disposition", contentDisposition);
FileInputStream input = new FileInputStream(filename);
ServletOutputStream out = response.getOutputStream();
IOUtils.copy(input, out);
input.close();
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
public static String filenameEncoding(String filename, HttpServletRequest request) throws IOException {
String agent = request.getHeader("User-Agent"); //获取浏览器
if (agent.contains("Firefox")) {
BASE64Encoder base64Encoder = new BASE64Encoder();
filename = "=?utf-8?B?"
+ base64Encoder.encode(filename.getBytes("utf-8"))
+ "?=";
} else if(agent.contains("MSIE")) {
filename = URLEncoder.encode(filename, "utf-8");
} else {
filename = URLEncoder.encode(filename, "utf-8");
}
return filename;
}
}

能力有限。写博客只为了防止自己忘记，方便查找，如有错误，还望指出

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